In order to alleviate a burden of hospital visit on a patient such as a diabetic requiring everyday medication, there have conventionally been available portable injectors for the patient to administer an injection by himself/herself in the home, workplace, and the like. For such an injector, a disposable cartridge-type injection needle has sometimes been used to prevent infection and the like caused by the secondary use of the injection needle (for example, refer to Patent Document 1).
The above-described conventional cartridge-type injection needle has problems as described below. That is to say, there arises a problem in that when the cartridge-type injection needle is mounted to or removed from an injector body, a needle stick accident may happen. Further, a used injection needle has a problem in that secondary infection caused by a needle stick accident and the like may occur.    Patent Document 1: Japanese Patent Laid-Open No. 8-66475